It’s a question he’s been considering for most of his career—but Cole is a genomics researcher, not a philosopher. To him, this question isn’t rhetoric or a thought experiment. It’s science—measureable and finite.

Cole, a professor of medicine and psychiatry at the University of California, Los Angeles, has spent several decades investigating the connection between our emotional and biological selves. “The old thinking was that our bodies were stable biological entities, fundamentally separate from the external world,” he writes in an email. “But at the molecular level, our bodies turn out to be much more fluid and permeable to external influence than we realize.”*

His latest project is the examination of happiness in biological terms. “There’s an intrinsic connection between our experience of life and the molecular function of our bodies,” he explains. Specifically, Cole and his team of researchers at UCLA have found that happiness may be linked to the function of immune cells.

As he explains, the immune system has two primary programs: one that fights viral infection, and one that fights bacterial infection and causes inflammation. The second function, known as the inflammatory response, has a downside: Its efforts to keep healthy immune cells circulating in the body can also cause tissue damage.

Cole has found that the balance of these two functions of the immune system may change based on life experiences. His work has shown that negative experiences like a new cancer diagnosis, depression, post-traumatic stress disorder, and low socioeconomic status are associated with increased activity of inflammation genes in immune cells. “Over the past 15 years, we have found that diverse social and psychological experiences that cause a sense of threat or uncertainty can evoke a similar response in our immune cells,” he says.

Listening to him explain his work is part philosophy lesson, part cellular-biology lesson, a scientific discourse on la dolce vita. “We're now beginning to ask how positive life circumstances might potentially counteract those negative threat effects at the molecular level. What are the concrete things we can do to actively promote more favorable gene expression profiles in the immune system?" he writes.

But how exactly do our immune cells register this abstract concept of happiness? The answer depends on how “happiness” is defined.

“Philosophers have long distinguished two distinct forms of happiness, hedonic well-being and eudaimonic well-being, and recent evidence suggests that they may have different biological correlates,” Cole writes. “Hedonic well-being is the type of happiness that comes from experiencing lots of positive emotions,” while eudaimonic well-being “is our sense of purpose and direction in life, our involvement in something bigger than ourselves.” Of the two terms, as Cole uses them in his research, eudaimonic well-being in particular is associated with a more favorable profile of gene activity in immune cells, according to Cole.

To determine this effect, Cole and a team of researchers from the University of North Carolina, Chapel Hill, asked 80 healthy adults to fill out questionnaires about their well-being. The researchers then analyzed the volunteers’ answers to assess their levels of eudaimonic and hedonic well-being, and took blood samples to study the functioning of their immune cells. They found that a high score of eudaimonic well-being, more than a high score of hedonic well-being, was correlated with a more favorable genetic expression profile, meaning the immune cells showed high levels of the antiviral response and low levels of the inflammatory response. The researchers posited that though both types of happiness were experienced as similarly positive, the corresponding genetic expression profiles were quite different. “When we asked people how happy they felt, both types of happiness seemed about the same,” Cole writes. “But when we looked at the cellular and molecular level, eudaimonic well-being had much more favorable molecular correlates than hedonic well-being.”

“We already know lots of ways to achieve hedonic happiness. The big question now is how can we evoke a more eudaimonic-linked profile in our immune system?” he continues.

But perhaps the most striking theory posed of meditation is that it could alter genetic material.

In recent years, a new field of study, known as mind-body genomics, has emerged. Among the most well-known researchers in this area are Nobel laureate Elizabeth Blackburn, a biochemist at the University of California, San Francisco, and her colleague, psychiatrist Elissa Epel. Through a seriesofstudies, the two found that meditation could affect the ends of DNA known as the telomeres, which act as protective caps for genes. The longer the telomere, the greater the protection conferred for the DNA strand, and the longer that cell can survive.

And telomeres, like immune cells, seem to respond to emotional cues. Negative external conditions like chronic stress that reduce eudaimonic happiness may shorten telomere length, while stress-reducing activities like meditation may help to maintain it. “Telomeres are affected by many things, but they are directly affected by stress. So we can see how improvements in our mental health, through the practice of meditation, might be linked to improvements in our telomeres,” Epel explains. “They offer us a window and some insight into how we are living, and help us appreciate how what we do today can affect our health tomorrow.”

As the field of mind-body genomics matures, the focus is moving towards gaining a better understanding of not only how DNA could be structurally changed by meditation, but also whether meditation can alter DNA functionally, through changes in how genes are expressed. In one recent study, for example, meditation was linked to enhanced expression of genes associated with insulin secretion, telomere structure, and cellular energy and function, and decreased expression of genes linked to inflammation and stress. What’s more, blood samples collected during the study found that experienced meditators showed changes in their genetic activity after just one meditation session.

With around 20,000 genes in the human genome, Cole, Epel, and other researchers have just scratched the surface of the connection between our emotional and biological selves. “We are an ever-changing conglomeration of cells very much influenced by our experience of the world around us,” Cole says. “At the rate we’re going, we have more data than we can make sense of. It’s this process that helps us get closer to understanding the black box. Who knows? Maybe in the future we may be able to sequence our own genes.” Epel agrees: “We don’t yet have the technology to monitor our telomeres, but it’s coming.”

In the meantime, though, the lessons of mind-body genomics still apply. “The experience you have today will influence the molecular composition of your body for the next 80 days, because that’s how long the average protein synthesized in your body today will hang around in the future,” Cole says. “So plan your day accordingly.”

* This and other quotes of Cole's have been updated for clarity and accuracy.

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Aditi Nerurkar is a physician and instructor at Harvard Medical School. She specializes in integrative medicine and stress management.